INTRODUCTION: Surgery is sometimes performed on patients with peau d'orange (dermal oedema) of the breast. This may be done to achieve local control of cancer after neo-adjuvant chemotherapy or in resectable locally advanced disease. Conventional practice is not to place excision lines through areas of peau d'orange for fear of recurrence in such an area. The question can be asked whether this wisdom is still valid in modern practice. No formal cohort studies documenting the histopathology of the skin in areas of peau d'orange have been published, and available descriptions are scanty. AIM: To describe the histopathological features of peau d'orange. METHOD: Consecutive patients undergoing mastectomy for cancer in whom peau d'orange was present were selected over a period of 2 years. Blocks of skin were excised from areas of peau d'orange and examined histologically. The presence, nature and location of malignant cells were recorded and correlated with lymph node pathology. Prior administration of neo-adjuvant chemotherapy was noted. RESULTS: Twenty-six mastectomy specimens were examined. Tumour islands in lymphatics were identified in 10 of the 26 specimens. These tumour groups were found in lymph vessels of both the superficial and deep dermal plexuses. In 1 specimen the presence of malignant cells was equivocal. Metastatic tumour was present in axillary lymph nodes in 19 of 22 specimens. Fourteen patients had been treated with neo-adjuvant chemotherapy, and 5 of their specimens exhibited the presence of tumour cell groups in lymphovascular channels. CONCLUSION: Tumour cells were present in the lymphatic vessels in areas of peau d'orange in 38% of the specimens studied. It would be expected that placing an excision line in such an area would result in an incomplete cancer operation in a high percentage of, but not all, cases.